Biofilms, which are defined as communities of microorganisms attached to a surface, are associated with chronic diseases of many human bacterial pathogens. The opportunistic pathogen Pseudomonas aeruginosa forms biofilms on a variety of surfaces including the lungs of cystic fibrosis patients, the mucosa of ear surfaces, and epithelial cells or catheters of the urinary tract. While there is a considerable amount of information regarding the molecular biology and genetics of P. aeruginosa biofilm development in vitro, little is known about how this opportunistic pathogen establishes infections that lead to biofilms and persistence in vivo. These knowledge gaps are due, in part, to the lack of suitable models for investigating biofilm-grown P. aeruginosa. The overall objective of this proposal is to develop a model system for evaluating P. aeruginosa pathogenesis and the host response during persistent diseases associated with biofilms. In aim 1, a chinchilla middle ear infection model will be developed. Experiments in aim 2 will determine if bacterial factors that contribute to biofilm formation and persistence in vitro are also associated with disease progression in the chinchilla middle ear infection model. Despite significant advancements in our knowledge of P. aeruginosa biofilm development in vitro, there remain gaps in our understanding of the in vivo relevance of such findings. This is due to the lack of suitable models for investigating the chronic and persistent aspects of P. aeruginosa pathogenesis. Development of such models may lead to a better understanding of the host-pathogen interface and lead to strategies to improve the quality of life for patients with P. aeruginosa infections that involve biofilms. Moreover, our long-range plan is for this project to serve as a foundation for a program project application targeted to NIH NIAID or NHLBI to investigate the host-pathogen interface in persistent infections. Biofilms, which are defined as communities of microorganisms attached to a surface, are associated with chronic diseases of many human bacterial pathogens. Pseudomonas aeruginosa forms biofilms on a variety of surfaces including the lungs of cystic fibrosis patients, the mucosa of ear surfaces, and epithelial cells or catheters of the urinary tract. This application seeks to develop a model system for studying P. aeruginosa pathogenesis and the host response during persistent diseases associated with biofilms. Development of such a model will lead to a better understanding of the host-pathogen interface and lead to strategies that improve the quality of life for patients with P. aeruginosa infections that involve biofilms.